books.google.ro - An important series of books that tells the dramatic stories behind the great discoveries of science. From the nature of the atom to the age of the universe, your students will read about the great scientists who asked the questions, and followed the process of discovery that helped us to understand...http://books.google.ro/books/about/How_Do_We_Know_the_Age_of_the_Universe.html?hl=ro&id=hvKzeJouZ9UC&utm_source=gb-gplus-shareHow Do We Know the Age of the Universe